The WildStar team has posted a provocative new article on the official site that discusses the ongoing 'battle' between MMOs as theme park or as sandbox environments. The article starts right off the contention that the WildStar team is attempting to make the game a true hybrid of the two.
We try to have both ways - I like examples, because they are clear. In most zones, there is an overall 'theme park' overlay - a main quest line that brings you through the zone, has some clear story to it, and is strongly directed. So you always have a guidepost for where you "need" to go (you can skip it, but most people do it). But in the same area, you can find random quests that are either dynamic (through discoveries, for instance), or some zones have elements like poachers who might get bored, build camps, and then there is a prisoner in the camp with a quest for you.
Read more on the WildStar site.